Peripheral sensory neurons are responsible for detecting chemical, thermal and mechanical stimuli in the skin. Their ability to recognize and process these touch sensations is influenced by the territories in which their peripheral arbors innervate the skin, how they connect in the central nervous system, and their ability to relay information to downstream circuits. Defects in any of these components can result in a range of debilitating disorders collectively known as peripheral neuropathies. Extensive research has gone into cataloguing the different subtypes of sensory neurons based on the expression of specific molecular markers. However, the mechanisms by which sensory neuron subtypes identify process and transmit different kinds of sensory information are still largely unknown. We have discovered that two subclasses of peripheral sensory neurons in zebrafish larvae can be distinguished by their pattern of axon projection into the central nervous system: some terminate in the hindbrain, whereas others terminate within the spinal cord. I propose to study how these sensory neurons'projection patterns correlate with their peripheral axon territory selection strategy, their behavioral function, and their pattern of activation of downstream interneurons. These studies should together provide insight into how neural circuits distinguish between sensory inputs. Aim 1: To characterize the territory selection strategy of a specific sensory neuron subtype. Aim 2: To determine if different subtypes of sensory neurons elicit distinct behavioral responses. Aim 3: To identify interneurons activated by specific subtyes of somatosensory neurons. Peripheral neuropathies can occur as secondary effects of various disorders and/or their treatments, while in most cases, they are idiopathic. Disease based trials of therapeutic drugs have advanced the treatment of certain peripheral neuropathies, but because somatosensory neurons are molecularly and functionally heterogeneous, effective treatments for one neuropathic disorder will not necessarily have the same effect for other disorders. Treating these disorders will require knowledge of how different sensory neuron subtypes process and discriminate sensory inputs.